Re: [PATCH] xen/passthrough: add missing error-report include

[Daniel P. Berrangé <berrange@xxxxxxxxxx>]

On Fri, Jul 18, 2025 at 03:20:35PM +0200, Markus Armbruster wrote:
> Daniel P. Berrangé <berrange@xxxxxxxxxx> writes:
> 
> > On Fri, Jul 18, 2025 at 07:59:50AM +0200, Markus Armbruster wrote:
> >> Markus Armbruster <armbru@xxxxxxxxxx> writes:
> >> 
> >> > Adam Williamson <awilliam@xxxxxxxxxx> writes:
> >> >
> >> >> In cfcacba an `error_report` was added to this file, but the
> >> >> corresponding include of `qemu/error-report.h` was missed. This
> >> >> only becomes apparent when building against Xen 4.20+.
> >> >>
> >> >> Signed-off-by: Adam Williamson <awilliam@xxxxxxxxxx>
> >> >> ---
> >> >>  hw/xen/xen_pt.c | 1 +
> >> >>  1 file changed, 1 insertion(+)
> >> >>
> >> >> diff --git a/hw/xen/xen_pt.c b/hw/xen/xen_pt.c
> >> >> index 9d16644d82..006b5b55f2 100644
> >> >> --- a/hw/xen/xen_pt.c
> >> >> +++ b/hw/xen/xen_pt.c
> >> >> @@ -54,6 +54,7 @@
> >> >>  
> >> >>  #include "qemu/osdep.h"
> >> >>  #include "qapi/error.h"
> >> >> +#include "qemu/error-report.h"
> >> >>  #include <sys/ioctl.h>
> >> >>  
> >> >>  #include "hw/pci/pci.h"
> >> >
> >> > Uh, error-report.h is included without this for me.  To see, build with
> >> > -H:
> >> >
> >> > . /work/armbru/qemu/hw/xen/xen_pt.h
> >> > .. /work/armbru/qemu/include/hw/xen/xen_native.h
> >> > ... /work/armbru/qemu/hw/xen/trace.h
> >> > .... ./trace/trace-hw_xen.h
> >> > ..... /work/armbru/qemu/include/qemu/error-report.h
> >> 
> >> Just remembered: the generated trace header includes error-report.h only
> >> when trace's log backend is enabled.
> >
> > Hmm, that's rather an unfortunate trap-door :-( Given that 'log' is enabled
> > by default when building from git we'll never see missing error-report.h
> > problems in daily work.
> 
> Correct.
> 
> > Looking at the log backend it appears that originally it would
> > unconditionally include the timestamp when calling qemu_log, but
> > then changed that to opt-in with
> >
> >   commit 418ed14268f797a5142b60cd557cd598eb548c66
> >   Author: Stefan Hajnoczi <stefanha@xxxxxxxxxx>
> >   Date:   Mon Jan 25 11:35:07 2021 +0000
> >
> >     trace: make the 'log' backend timestamp configurable
> >
> > requiring -msg timestamp=on, which was a pre-existing flag that already
> > did a similar toggle for the 'error_report' function. The goal makes
> > sense, but it introduced the error-report.h trap door
> >
> > When I see that I also question why the 'log' backend should be a
> > special case user of qemu_log() ?  Why shouldn't we emit timestamps
> > for all usage of qemu_log() ?
> >
> > If we changed the qemu_log impl to honour the timestamp toggle, then
> > all users of qemu_log benefit. We then eliminate error-report.h usage
> > in trace.h headers, and also cut the code size for trace points
> > significantly
> >
> >
> > static inline void _nocheck__trace_object_dynamic_cast_assert(const char * 
> > type, const char * target, const char * file, int line, const char * func)
> > {
> >     if (trace_event_get_state(TRACE_OBJECT_DYNAMIC_CAST_ASSERT) && 
> > qemu_loglevel_mask(LOG_TRACE)) {
> >         if (message_with_timestamp) {
> >             struct timeval _now;
> >             gettimeofday(&_now, NULL);
> >             qemu_log("%d@%zu.%06zu:object_dynamic_cast_assert " "%s->%s 
> > (%s:%d:%s)" "\n",
> >                      qemu_get_thread_id(),
> >                      (size_t)_now.tv_sec, (size_t)_now.tv_usec
> >                      , type, target, file, line, func);
> >         } else {
> >             qemu_log("object_dynamic_cast_assert " "%s->%s (%s:%d:%s)" 
> > "\n", type, target, file, line, func);
> >         }
> >     }
> > }
> >
> > down to
> >
> >
> > static inline void _nocheck__trace_object_dynamic_cast_assert(const char * 
> > type, const char * target, const char * file, int line, const char * func)
> > {
> >     if (trace_event_get_state(TRACE_OBJECT_DYNAMIC_CAST_ASSERT) && 
> > qemu_loglevel_mask(LOG_TRACE)) {
> >             qemu_log("object_dynamic_cast_assert " "%s->%s (%s:%d:%s)" 
> > "\n", type, target, file, line, func);
> >     }
> > }
> >
> > which feels more in keeping with the kind of level of complexity you should
> > want to be inlined in trace callers.
> 
> Oh yes.  We should do this even if we find a reason for keeping
> qemu_log() as it is.  The obvious way would be a new function
> qemu_log_with_timestamp().

Now proposed at:

  https://lists.nongnu.org/archive/html/qemu-devel/2025-07/msg05234.html

With regards,
Daniel
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